Type 1 diabetes (T1D) is a T cell mediated autoimmune disease where the breakdown of self tolerance to islet beta cell antigens leads to immune mediated islet destruction, loss of insulin production and hyperglycemia. Development of immunotherapies that restore self tolerance may prevent T1D or even reverse this disease. Immature dendritic cells (iDCs) are regarded as tolerogenic DCs, and have been intensively investigated for DC-based immunotherapy of various autoimmune diseases including type 1 diabetes (T1D). However, the roles of the antigenic epitopes presented by iDCs have drawn less attention. In T1D, it has been demonstrated that different 2 cell antigens play different roles in T1D pathogenesis. It is, therefore, of great interest to investigate the roles of different 2 cell antigenic epitopes presented by iDCs in T1D prevention. Because of the difference in natural antigen presentation between dominant determinants and cryptic determinants, the T cell pools specific to different antigen determinants of a 2 cell antigen will be different at different disease developmental stages. In other words, the naive T cell pools for dominant determinants will become smaller and smaller and finally exhausted with disease progression because the naive T cells to dominant determinants are increasingly primed to antigen-specific effector or memory T cells, whereas, naive T cell pools for cryptic determinants remain the same at different disease stages because those cryptic determinants will never be presented to the antigen-specific T cells naturally. Therefore, the requirements for iDCs presenting 2 cell dominant determinants and cryptic determinants for tolerance induction would be different. In this study, we will attempt to determine the roles of iDCs pulsed with 2 cell antigen dominant determinants or cryptic determinants inT1D prevention. Three specific aims are proposed: 1. To determine the in vitro CD4+ T cell-priming activities of DCs presenting 2 cell antigen dominant or cryptic determinants;2. To assess the effect of DCs pulsed with 2 cell dominant or cryptic determinants in T1D prevention;3. To characterize the mechanisms underlying the T1D protection by 2 cell peptide-pulsed iDCs. This study is of great significance for developing more effective 2 cell antigen-based immunotherapies. To our knowledge, this is the first to investigate the roles of different 2 cell antigenic epitopes in DC-based T1D immune intervention. Since human 2 cell dominant and cryptic determinants have been described, the research data attained in this pre-clinical study will guide the ongoing clinical trials for human T1D DC-based immunotherapy, and will play an important part in further developing more effective DC-based antigen therapy for human T1D. PUBLIC HEALTH RELEVANCE: This proposal is to investigate the roles of beta cell antigen dominant determinants and cryptic determinants in dendritic cell-based T1D immunotherapy. The results of this study will help develop more effective immunotherapeutic approaches for human type 1 diabetes.